The present invention relates to dental apparatus, and more particularly to a simplified system for transferring dental-facial information from a patient to a dental articulator to facilitate accurate mounting of dental study casts on the articulator for the diagnosis and treatment of both aesthetics and function.
In analyzing and treating jaw disorders and in making dental prostheses, it is desirable to simulate the patient""s jaw movements. To do this on a dental articulator, it is first necessary to analyze the jaw movements and then transfer the information to a dental articulator to enable the articulator to move in a manner to simulate the patient""s jaw movements. This enables the dentist or technician to test and shape dental prostheses on the articulator before mounting them in the patient""s mouth.
In one system for analyzing jaw movements, an upper frame or face bow is mounted on a patient""s nose and ears with side arms supporting rigid recording plates overlying the patient""s temporomandibular joints. A grid of intersecting lines on graph paper is provided on the recording plates. A lower or mandibular frame is mounted by means of a dental clutch to the patient""s lower jaw so as to move with the jaw with side arms of the lower frame carry writing elements for tracing jaw movements on the graphs.
In use of such apparatus, it is usually initially necessary to locate the hinge axis about which the lower jaw rotates when it is in its rearward most position, and moved in mouth closing and opening directions. Once the hinge axis is located, the jaws are moved in various fashions to provide tracings with respect to a reference line through the hinge axis and a point on the patient""s nose or face. The data obtained from the tracings is then used to set a dental articulator.
There are a variety of other systems explained in the literature for obtaining information about the jaw movements, all of which have various complexities and disadvantages.
In mounting dental casts to an articulator, it is necessary to position the cast in the same relation to each other as the teeth in the patient""s mouth as well as being orientated or related to the patient""s hinge axis. In accomplishing that, impressions of the patient""s bite are made in impression material positioned on a flat bite fork which is clamped between the patient""s upper and lower teeth. The position of the bite fork in relation to a reference plane on the patient is determined using an arbitrary axis face bow also known as an ear-bow, and the bite fork is then mounted on the lower frame of the dental articulator in a position to receive the upper dental cast of the patient""s teeth. These so-called different reference planes has been referred to as xe2x80x9cFrankfort-horizontal,xe2x80x9d xe2x80x9caxis-orbital,xe2x80x9d or xe2x80x9caxis-horizontalxe2x80x9d plane of reference. The arbitrary face bow is related to an average distance from the axis of the lower jaw to the ear hole (auditory meatus) to a third point of reference located somewhere on the patient""s face. While the cast is held in that position, it is secured by dental plaster to a mounting plate attached to the upper frame of the dental articulator. Once the upper cast is mounted, the lower cast can be secured to the articulator by utilizing the upper cast as a guide along with an interocclusal record.
While these known systems are relatively accurate, they are unfortunately still somewhat complicated and time consuming, requiring many different steps, comprising many components including screws to tighten and bite forks that need to be sterilized before each use. These systems are also related to an average axis-to-earhole distance. As a result, many practitioners do not use a dental articulator but instead employ old manual techniques, and trial and error, or allow technicians to mount into small disposable dental articulators without regard or relation to the hinge axis or lateral movements, in terms of providing proper function and fitting of prostheses on the patient. It is believed that many more practitioners would utilize a dental articulator if the procedures for obtaining patient dental-facial information and mounting that information in a dental articulator were greatly simplified.
In providing dental prostheses, it is only in recent years that more attention is being paid to improving the aesthetic aspects of a patient""s teeth at the same time that the functional aspects are being performed or improved. Thus, it is desirable that not only a simplified system for increasing the use of dental articulators, but it is also desirable that the aesthetic aspects be properly addressed.
Briefly stated, the invention is directed to a system, including apparatus and method, for orienting a patient""s bite, capturing or registering in bite registration material the tilt or slant of the occlusal plane of the patient""s teeth in three planes of space in relation to the cranium or head and related to an average or specific axis-incisal distance. The registration material is on an index tray positioned on a horizontal face bow analyzer. The invention further includes an adjustable mounting platform on the lower frame of a dental articulator adapted to receive the index tray from the analyzer bow to mount study casts on a dental articulator.
If a patient specific axis-incisal distance is to be used, the operator measures the distance from the patient""s approximate hinge axis to the maxillary incisors. The patient""s bite is then formed in the registration material on the index tray aligned with marking, such as a line, indicating the forward edge of the patient""s incisors. The distance between the line marked on the index tray on the mounting platform and the hinge axis defined in the dental articulator is related to the distance between the patient""s incisal edge and the patient""s jaw hinge axis. The distance between the articulator hinge axis and the incisal line marked on the index tray on the mounting platform is equal to the average 100 mm corresponding distance for patients. More preferably, the patient""s specific axis incisal distance measured previously is marked on the index tray from the average 100 mm line. Or, the mounting platform can be adjustable in an anterior posterior position, that will correlate more closely with measured data obtained from the patient. Further, the platform is preferably vertically adjustable so as to position the selected incisal line at a consistent horizontal distance with respect to the hinge axis and to center the study casts in the articulator.
The face bow analyzer includes a bite fork portion and a pair of gripping wings or handles flaring outwardly from a central portion, protruding forwardly from the bite fork, and wrapping around the patient""s face. The forward portion is formed with an elongated slot for receiving a vertical indicator rod. The rod is supported in a holder that is slidably mounted in the slot to enable the rod to be moved close to the patient""s face. Preferably, the analyzer face bow is a one-piece thin flat rigid element.
In use, an average value of 100 mm can be used, or preferably, the operator can measure the patient""s axis-to-incisal distance and mark the distance measured from the average 100 mm incisal line marked on the index tray. The upper and lower index trays are clamped to the bite fork on the analyzer bow and bite registration material is applied on the trays. The operator then grips the wings on the analyzer bow and inserts the bite fork into the patient""s mouth and aligns the maxillary central incisors to the incisal line marked on the upper index tray, while the patient is sitting erect looking straight forward. The indicator rod is then moved rearwardly towards the face, and the dentist adjusts the face bow so that the indicator rod appears vertical and aligned with the patient""s midsagittal when viewed from the front. The patient is lightly gripping the impression material on the trays, but the trays are still movable within the impression compound. The operator then views the analyzer bow from the side to get a profile view, and manipulates the bow so that the indicator rod is vertical from that perspective. A level gauge can be added to the analyzer bow to verify the horizontal relation of the bow. The analyzer bow is then horizontally oriented, capturing the patient""s tilt or slant of the occlusal plane in relation to the patient""s cranium in three planes of space related to an average or specific axis-incisal distance. With the analyzer bow so positioned, the bite registration material is allowed to set or harden.
Once the material has set, the operator can position the O-rings on the vertical indicator rod to different facial landmarks, such as eyes, nose and chin for diagnosing the patient""s facial proportions. The height of the right and left lip commisures can also be measured from the index tray and noted in the patient""s chart for future reference to be transferred to the study casts on the articulator.
Following that, the operator, gripping the wings on the bow, carefully removes the bite fork from the patient""s mouth, and the upper index tray is removed and sent to the laboratory for positioning on the mounting platform supported on the dental articulator to mount the patient""s upper cast to the upper frame of a dental articulator. This is done by attaching an adjustable mounting platform, configured to receive upper index tray, to an articulator with the hinge axis related to an incisal line on the index tray. The mounting platform is vertically adjustable with a millimeter scale, that can be set to a desired incisor length.